This invention is directed to a portable, fire suppression system, wherein a foamable liquid and a non-flammable compressed gas are combined in a manifold to generate foam.
It is well known that the application of foam is useful to suppress fires. The foam is generated at the site of the fire, typically by mixing together a stream of water containing a suitable foaming agent and air. The quality of the foam, the liquid to gas ratio of the foam, the ability to use non-combustible gases, and the distance that the foam can be sprayed are factors relevant to the design and operation of fire suppression equipment.
Carroll et al., U.S. Pat. No. 5,058,809 is representative of a foam generating nozzle designed to aspirate ambient air into a flowing aqueous stream containing a foam producing agent. Foam is produced and discharged from the outlet of the nozzle. It is also known to incorporate a deflection or impingement structure in a foam-generating nozzle to facilitate mixing and increase foam production, as shown in Nysted, U.S. Pat. No. 4,330,086.
There are a number of drawbacks associated with foam generating nozzles. Since air contains oxygen, foam generated from using air as the gas is not ideal for smothering a fire. Also, many of the nozzles operate as ejectors, that is, the kinetic energy of the flowing aqueous stream is used to draw air into the nozzle. The principle of conservation of momentum results in a decrease in the velocity of the aqueous stream. Furthermore, deflection and impingement structures provided in the nozzle can increase the resistance to fluid flow through the nozzle.
Urquhart et al., U.S. Pat. No. 2,106,043 disclose a method for generating foam in which a non-combustible gas is mixed with an aqueous foam forming mixture in a foam forming chamber. The entering gas is distributed in the foam forming chamber under pressure, wherein the pressure of the gas is sufficient to carry the foam from the chamber through the hose and nozzle attached thereto. The gas is introduced perpendicular to the flow of the aqueous mixture.
Foam-generating devices having a mixing manifold, in which the gas is injected at an angle of less than 90° relative to the flow direction of the foam forming liquid solution, are disclosed in Mahrt, U.S. Pat. No. 5,881,817 and Henry, U.S. Pat. No. 6,112,819. Neither of the aforementioned references, however, contains jets or other means to increase the velocity of the foam-forming liquid, prior to the foam-forming liquid making contact with the gas being injected into the mixing manifold.